Motor control system



April 27, 1937. N. H. WILLBY MOTOR CONTROL SYSTEM 1 Filed Jan. 4, 1936 INVENTOR Norman H WZ/Zby.

FEEL

WITNESSES- AWN Patented Apr. 27, 1937 PATENT OFFICE 2,078,848 MOTOR CONTROL SYSTEM Norman E. Willby, Irwin, Pa., assignor to Wash inghouse Electric .2 Manufacturing Company, East Pittsburgh, -Pa., a corporation of Pennsyl- Vania Application January 4, 1936, Serial No. 57,557

Claims.

My invention relates, generally, to motor control systems and more particularly to systems for controlling the acceleration and the deceleration of electrically propelled vehicles.

for automatically releasing a magnetic tre/Jlr.

brake at a predetermined speed of an an elcc trically propelled vehicle.

A further object of my invention is to provide for coordinating the operation of dynamic V rrak= ing and magnetic track braking systems.

Other objects of my invention will he explained fully hereinafter or will be apparent to those skilled in the art.

According to the preferred embodiment of my invention, both the acceleration and the deceleration of the propelling motor of an electric vehicle are controlled by an accelerator of the type described in Patent No. 1,991,229, issued Febru ary 12, 1935, to L. G. Riley, and assigned to the Westinghouse Electric & Manufacturing Company. The accelerator utilized in the present system comprises a circular copper bus inside of which are disposed a plurality of contact fingers which are progressively forced against the bus by a revolving roller driven by a pilot motor. The contact fingers are connected to a resistor for controlling the current in the motor armature circuit both during acceleration and dynamic braking. The resistor is so connected in the armature circuit that the revolving roller is driven in one direction during acceleration of the motor and in the opposite directioniduring dy- I iiarnic braking. Deceleration of the vehicle is also caused by means of a magnetic track brake, the operation of which is coordinated with the dynamic braking system to produce smooth deceleration of the vehicle. For a fuller understanding of the nature and objects of the invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawing, in which:

Figure 1 is a diagrammatic view of a control system embodying the invention; and

Fig. 2 is a chart, showing the sequence of operation of a portion of the apparatus illustrated in Fig. l.

Referring to the drawing, electric motors I63 and it may be utilized for propelling a vehicle (not shown). The-motor ill is provided with an armature winding 2, a series field winding l3 and a separately excited field winding it. Likewise, the motor l l is provided with an armature winding E5, a series field winding l6 and a separately excited field winding ii. The field windings M and are utilized during dynamic braking to insure that the braking action will take efifect ouiclriy.

[an electrically operated line switch LS is pro video, for connecting motors iii and to a troliey i which engages a power conductor i9 that may he energized from any suitable source of port-er, such as a generating station (not shown The energization of the separately exwindings i i and ll is controlled by 2.

switch T which is closed to connect these field windings to the trolley 68 during coasting and dynair c oraring of the vehicle.

Both acceleration and the deceleration of the motors and is primarily controlled by a motor-driven accelerator A which is of the same general type as the one described in the aforementioned Patent No. 1,991,229. The accelerator A comprises a circular copper bus 28 inside of which are disposed a plurality of contact fingers. to inclusive, which are progressiveiy forced against the bus 23 by a revolving roller roller is driven by a pilot motor t l through shafts and t6 connected by bevel gears ll. The pilot motor 34 is provided with an armature winding and two field windings and one for each direction of rotation. A spring actuated brake M is provided for stopping the motor 36, a brake release coil 52 being connected series with the armature winding of the pilot motor and deenergized when the motor is deenergized.

The accelerator is proidded with a resistor 53 that is divided into a number of sub-divisions which are connected to the contact fingers 2! to 2, inclusive. A major portion of the resistor 33 is connected in the armature circuits of the motors it: and l i and is utilized to control the armature current during acceleration of the vehicle. The entire resistor 53 may be utilized to control the current flowing in the motor circuit during dynamic braking.

As shown, a number of cam-switches Al, A2,

l performing certain switching operations.

A3. A4, B, C, D, E, F, and H are located in the accelerator and are actuated by the shaft 46. The reference numerals II to 42'. inclusive, indicate the contact fingers over which the roller 43 travels while the cam switches are closed. The function of the various cam switches will be explained more fully hereinafter.

In addition to the accelerator and the cam switches, several other switches are provided for These switches include a switch Ml for connecting the motors II and ii to the resistor 53 during acceleration, a switch M2 for connecting one terminal of the motors directly to ground after a major portion oi the resistor has been shunted from the motor circuit by the accelerator roller it, switches BI and B! for establishing dynamic braking connections for the motors Ill and II, and a switch 'I'Bl for controlling the operation of a magnetic track brake TB, which is provided for eflecting the deceleration of the vehicle in conjunction with the dynamic braking action of the motors I! and II.

Drum controllers MC and BC are provided for controlling the motor connections during acceleration and braking, respectively. The controllers are electrically interlocked to prevent improper operationof the equipment.

0 gization of the track brake TB by shunting a resistor 54 from the energizing circuit for themagnetizing coil of the magnetic brake.

A current limit relay L functions in the usual manner to limit the motor current. both durin acceleration and dynamic braking, by regulating the operation of the accelerator A. The contact members of the limit relay are disposed to shunt the armature of the pilot motor 44 when closed, thereby stopping the accelerator.

In order to prevent a sudden rush of current upon the re-application of power or dynamic braking after coasting of the vehicle, a spotting relay SR is provided to change the position of the accelerator roller during coasting to approximately match the car speed. The shunt field windings H and ll of the motors i0 and II, respectively, are energized during coasting by the closing of the switch T to connect the shunt field windings to the power conductor it. Therefore, the motors develop a voltage which is proportional to the speed of the car.

Since the actuating coil I! of the relay SR is connected across the armature of the motor H, the relay is responsive to the speed of the car. As the speed decreases, the contact members of the relay are closed, thereby causing the pilot motor 44 to return the accelerator roller toward the first contact finger. The backward movement of the accelerator operates one of the cam switches Al, A2, A! or Al to cut a portion of a resistor 56 out of the relay coil circuit. The con-.

tact members of the relay are then opened holding the accelerator until the car speed has been further reduced, when the accelerator is again moved backward by the closing of the relay contacts. This operation is repeated until the master controller is moved out of the coasting position, or until the accelerator is returned to the first position.

As stated hereinbefore, the switch TB! is provided for deenergizing the magnetic track b'rake TB when the yehicle has been slowed down to a predetermined speed. In order that the deenergization of the track brake will be responsive to the speed of the vehicle, provision is made for The braking controller BC is also utilized to control the enershunting the actuating coil ll of the switch 'I'Bl through a circuit having a resistance proportional to the voltage of the motors during dynamic braking. which voltage is proportional to the speed of the vehicle. Thus, the switch TBI is automatically opened to deenergize the track brake when the car is slowed down to a predetermined speed, and the car may be brought to a complete standstill and held there by means of the usual air braking system. In this manner, the possibility of the magnetic track brake being inadvertently left energized while the car is stopped is prevented. Furthermore, smoother deceleration of the vehicle is obtained by avoiding the tendency of the track brake to cause a sudden stopping or jerking of the car when it is moving at a slow speed.

In order that the functioning of the foregoing apparatus may be more clearly understood, the

operation of the system will now be described in more detail. Assuming that a control switch I has been closed, the motors IO and i i may be connected to the power source to start the vehicle by actuating the master controller MC to position 41" to close the switch LS and MI. The energizing circuit for the actuating coil of the switch IS may be traced from a power conductor .2. which is connected to the trolley ll, through the control switch 6|, conductor .8, contact fingers 6t and 65, bridged by a contact segment I on the master controller MC, conductor 81, an interlock GI on the switch B2, conductor I, the actuating coil H of the switch LS. and conductor 12 to the grounded conductor I3. The energizing circuit for the actuating "coil of the switch Ml extends from the previously energized conductor 09 through the actuating coil 14 of the switch Ml and conductor I2 to the grounded conductor II.

The closing of the switches LS and MI connects the motors l0 and II to the power source in parallel circuit relation and in series with a major portion of the resistor 53 in the accelerator A. The circuit through the motor i. may be traced from the power conductor 02 through contact members 15 of the switch LS. conductors I6 and II, the armature winding l2. series field winding l3, conductor ll, contact members ll of the switch Ml. conductor II, the resistor '3. contact finger 2|, which is compressed against the bus 20 by the roller 41 and conductor '2 to the grounded conductor 13. The circuit through the motor ll extends from conductor 11 through the series field winding it, the armature winding IS, the actuating coil 88 of the limit relay L to conductor 18 and thence through the circuit previously traced to the grounded conductor I3. Since the resistor 53 is connected in series with the motors, the vehicle will be operated at a slow rate of speed.

If it is desired to accelerate the vehicle. the master controller MC' may be actuated to position 12", thereby energizing the pilot motor 44 which operates the roller U to cut the resistor coil 52 of the brake 51, and conductor ll to the grounded conductor I3. As explained hereinbefore, the energiz'ation of the coil '2 releases the brake 5| which permits the motor 44 to opcrate the accelerator A.

The rotation of the roller 43 compresses the contact fingers on the accelerator against the bus 20.to shunt the resistor 53 from the motor circuit as described hereinbefore. The shunting of a portion of the resistor 53 will permit the motor current to increase to a value-which will operate the limit relay L to establish a shunt circuit around the armature of the motor 44 and the brake release coil 52, thereby stopping the acceleratoNThe shunt circuit may be traced from one terminal oi the armature 48 through conductor SI. contact members 92 on the limit relay L, and conductor 33 to the grounded conductor I3. When the main motors have accelerated to a speed which will cause the motor current to be reduced to a value that will permit the'limit relay L to open its contact members, the pilot motor 44 advances the accelerator to cut more resistance out of the main motor circuit. thereby causing the motors to be accelerated still further.

This operation is continued until the accelerator roller 43 reaches contact finger 33; at which time the .cam switch D is closed to energize the actuating coil of the switch M2. The energizing .circuit for the coil of the switch M2 may be traced from the previously energized conductor 69 through the actuating coil 94. conductor 95, the cam switch D and conductor 96 to the grounded conductor I3. The closing of the switch M2 connects the motors I and ii directly to ground through conductor 81, contact members 98 of the switch M2 and conductor 99 to the grounded conductor I3, thereby causing maximum voltage to be applied to the motors.

However, the pilot motor 44 will continue to advance the roller 43 to contact finger 42 in order that the full amount of the resistor 53 will be available for controlling the motor cur rent during dynamic braking of the motors. The advancement of the roller 43 is stopped by the opening of the cam switch B to deenergize the pilot motor 44.

Assuming that it is desired to permit the vehicle to coast. the master controller MC may be actuated to the off position, thereby opening the switches LS, MI and M2 to disconnect the motors I0 and Il from the power source. At this time, the switch T is closed to connect the field windings I4 and H to the power source. thereby separately exciting these windings and causing the motors I0 and II to generate a voltage proportional to the speed of the vehicle. The energizing circuit for the actuating coil of the switch T may be traced from a contact finger ii! i. which engages the contact segment 68. through con-' ductor I02, actuating coil I33 of the switch T, conductorv I04, the cam switch F and conductor 96 to the grounded conduct-or E3. The circuit through the field windings I4 and I1 may be traced from the power conductor 52 through conductor I05, the contact members I05 of the switch '1, conductor I01, field winding H, a re- When the vehicle is coasting at a relatively high speed, energization of the relay SR causes its contact members to be opened and the accelerator roller 43 remains on the last contact finger 42. As the speed of the vehicle decreases, the voltage produced by the motor II will decrease ,and the contact members of the relay SR are permitted to close, thereby causing the pilot motor 44 to operate the roller 43 in a counterclockwise direction. 'I'he energizing circuit for the pilot motor 44 may be traced from a contact finger. H8 on the master controller MC through conductor H9, contact fingers I2! and I22, bridged by a contact segment I23 on the braking controller BC, conductor I24, an interlock I25 on the switch T, conductor I26, contact members I2'I on the relay SR, conductors I23 and I29, contact fingers I3i and I32, bridged by a segment I33 on the controller MC, conductor I34, the cam switch C on the accelerator A, conductor i35, the field winding Slland the armature winding 48 of the pilot motor 44, conductor 81, the brake release -coil 52 and conductor 83 to the grounded conductor l3.

As described hereinbefore, the backward movement of the accelerator A causes the cam switch A4 to cut a portion of the resistor 56 out of the circuit for the actuating coil of the spotting relay SR, thereby causing the contact members of the relay to be opened to stop the accelerator until the speed of the vehicle has decreased still further, when the foregoing operation is repeated. In this manner, the spotting relay SR and the cam switches Al to A4, inclusive, cooperate to match the position of the accelerator roller with the speed of the vehicle, thereby insuring that the proper amount of resistance 53 will be available to control the motor current in the event that dynamic braking is established or power is reapplied to the motors I0 and I i by reconnecting them to the power source.

If it is desired to decelerate the vehicle by means of dynamic braking, the. braking controller BC may be actuated to one of the braking positions to close the switches BI and B2 to establish the dynamic braking connections provided the controller MC is in the off position. The

energizing circuit for the actuating coil of the switch BI may be traced from a contact finger i36, which engages the contact segment I23 of the braking controller BC, through conductor I 31, an interlock I38 on the switch LS, conductor I39, the actuating coil I of the switch Bi, conductor I42, the cam switch E, and conductor 55 to the grounded conductor I3. A holding circuit for the coil I is established through an interlock I43 by the closing of the switch BI. The holding circuit may be traced from the conductor 342 through the interlock I43 and conductor I2 to the grounded conductor 13. The energizing circuit for the actuating coil of the switch B2 extends from the previously energized conductor I39 through the actuating coil I44 of the switch B2 and conductor I2 to the grounded conductor I3.

The closing of the switches BI and B2 establishes dynamic braking connections for the motors I5 and II whereby the series field winding oi one motor is connected across the armature winding of the other motor in a manner to cause the motors to function as generators to retard the 5 movement 01 the vehicle. The circuit for the motor I may be traced from one terminal of the armature winding I2 through conductor 11, the field winding I5 0! the motor II, conductor I45, contact members I45 of the switch B2, conductor I41, the resistor 55, the contact finger 42, assuming that the accelerator roller 45' is on i the finger 42, the bus 20, conductors 52 and 15,

contact members I45 of the switch BI and conductor I49 to the other terminal of the armature l5 winding I2. The circuit for the motor II may be traced from one terminal of the armature winding I5 through conductor I45, the contact members I45 of the switch B2, conductor I", the

resistor 53, contact finger 42, the bus 20, conductors 52 and 15, the contact members I of switch BI, conductor I49, the field winding I5 of the motor Ill, conductor 15, and the actuating coil of the limit relay to the other terminal of the armature winding I5.

Since the switch T was closed when the master controller MC was actuated to the oiP position, the field windings I4 and I1 01' the motors I0 and II, respectively, are also energized at this time, thereby insuring that the circulating current 30 builds up rapidly and the dynamic braking action takes eiTect quickly. The braking current is controlled by means of the accelerator resistor 55 in the same manner as during acceleration oi the motors, the operation of the pilot motor being under control of the limit relay L. The pilot motor 44 is operated in a direction to cause the accelerator A to decrease the resistance in the dynamic braking circuit as the speed of the vehicle decreases. The energizing circuit for the pilot motor 44 extends from contact finger I5I on the braking controller BC which is connected to the conductor I25 and thence to the pilot motor 44 through the circuit previously traced.

If it is desired to utilize the magnetic track brake TB to aid the dynamic braking action of the motors I0 and II in stopping the vehicle, the braking controller BC may be actuated to a position in which the magnetizing coil of the track brake is energized. Since the switch T has been previously closed, an energizing circuit is established for the actuating coil of the switch TBI. Therefore, this switch is closed at this time. The circuit for the coil of the switch TBI may be traced from the power conductor 52 through conductor I05, contact members I05 0! the switch T, conductor I01, a resistor I52, conductor I55, the actuating coil 51 oi the switch TBI and conductor I54 to the grounded conductor 15.

The closing of the switch TBI establishes an energizing circuit for the magnetizing coil of the track brake TB, provided the braking controller BC is actuated to a position to energize the track brake. The closing of the switch TBI also establishes a holding circuit for the actuating coil of the switch T. This circuit may be traced from conductor I04 through conductor I55, an interlock I55 on the switch TBI, conductors I51 and 85 to the grounded conductor I5.

When the braking controller BC is actuated to a position in which its contact segment I55 bridges contact fingers I55 and I5I, the magnetizing coil of the track brake TB is connected across the power source in series with the resistor 54 through a circuit which extends from the control switch 5I through conductor I52, contact fingers I55 and I5I bridged by the segment I55, the resistor 54, conductor I55, contact members I54 on the switch TBI, conductor I55, the magnetizing coil I55, and conductor 55 to the grounded conductor 15.

If it is desired to increase the efiect ot the magnetic track brake, the braking controller BC may be advanced to shunt the resistor 54 from the circuit for the magnetizing coil of the track brake. thereby increasing the magnetizing efiect oi the coil and the braking action of the track brake. The resistor 54 may be shunted step-by-step by actuating the controller BC to cause the contact segment I55 to be successively engaged by the contact fingers I51 to I10, inclusive.

In order that the magnetic track brake TB will.

be completely deenergized when thevehicle has slowed down to a predetermined speed. provision is made for establishing a shunt circuit around the actuating coil 51 of the switch TBI through the armature winding of the motor I 0. Since the voltage developed by the motor I5 during dynamic braking is proportional to the speed of the vehicle, the effective resistance of the shunt circuit around the actuating coil 51 is also proportional to the speed of the vehicle. As the speed of the vehicle decreases, the eii'ectiveresistance oi the shunt circuit around the coil 51 is gradually decreased until there will be insuificient current flowing through the coil 51 to hold the switch TBI closed.

when the contact members of the switch are opened, the milgnetizing coil of the track brake TB is deenergized, thereby preventing the coil from being left energized alter the vehicle has been stopped. The shunt circuit around the coil 51 may be traced from the conductor I55 through conductor Hi, the cam switch H. conductor I12, contact fingers I15 and I14 bridged by contact segment I15 of the master controller MC, conductor I11, resistor I15, conductor 11, the armature winding I2 of the motor I5, conductor I45, and contact members I45 of the switch BI to the grounded conductor 15.

Thus, it will be seen that when the voltage of the motor I2 decreases to a predetermined value, the actuating coil 51 oi the switch TBI will be by-passed to ground through a circuit having a lower resistance than the circuit through the actuating coil 51, which will cause the switch TBI to be opened as previously described. The vehicle may be brought to a complete standstill by means of the usual air braking system (not shown).

From the foregoing description, it is apparent that I have provided for coordinating the operation of a dynamic braking system and a magnetic track brake to quinly and smoothly decelerate an electrically propelled vehicle. Also, it is apparent that I have provided for automatically releasing a magnetic track brake at a predetermined speed of the vehicle, thereby preventing an excessive use of electric power for operating the track brake and also preventing injury to the magnetizing element of the brake.

Since many modifications may be made in the apparatus and arrangement of parts without departing from the spirit of my invention, I do not wish to be limited other than by the scope of the appended claims.

I claim as my invention:

1. In a motor control system, in combination. a motor for propelling a vehicle, means for establishing dynamic braking connections for the motor, a magnetic track brake i'or decelerating the vehicle, and means responsive to the speed oi the vehicle during dynamic braking for deenergizing the track brake. 2. In a motor control system, in combination, a motor for propelling a vehicle, switching means for establishing dynamic braking connections for the motor, a magnetic track brake for decelerating the vehicle, control means for controlling the operation of said switching means and the energization of the magnetic track brake, and means responsive to the speed oi the vehicle during dynamic braking for deenergizing the track brake.

3. In a; motor control system, in combination, a motor for propelling a vehicle, switching means for establishing dynamic braking connections for the motor for decelerating the vehicle, a magnetic track brake for aiding in the deceleration of the vehicle, and means responsive to the voltage of the motor during dynamic braking for deenergizing the track brake.

4. In a motor control system, in combination, a motor for propelling a vehicle, switching means for establishing dynamic braking connections for the motor tor decelerating the vehicle, a magnetic track brake for aiding in the deceleration oi the vehicle, control means for coordinating the operation of the dynamic braking means and said magnetic track brake, and means responsive to the voltage of the motor during dynamic braking for deenergizing the track brake.

5. In a motor control system, in combination, a motor for propelling a vehicle, switching means for establishing dynamic braking connections for the motor for decelerating the vehicle, a mag-. netic track brake for aiding in the deceleration ofthe vehicle, and switching means for controlling the energization oi the magnetic track brake, said switching means being responsive to the voltage of the motor during dynamic braking.

40 8. In a motor control system, in combination,

a motor for propelling a vehicle, resistance varying means for controlling the motor current during acceleration of the vehicle, switching means for establishing dynamic braking connections for 45 the motor to decelerate the vehicle, said resistance varying means being utilized to control the motor current during dynamic braking, a magnetic track brake for aiding in the deceleration of the vehicle, switching means for controlling the energization 50 o! the magnetic track brake, and switching means associated with said resistance varying means ior controlling the operation of said switching, means for controlling the energization oi the} l magnetic track brake.

"I. In a motor control system, in combination, a motor for propelling a vehicle, resistance varying means for controlling the motor current dur ing acceleration of the vehicle, means !or exciting the motor during coasting of the vehicle, switch ing means for establishing dynamic braking connections for the motor to decelerate the vehicle, said resistance varying means being utilized to control the motor current during dynamic braking, and means responsive to the voltage of the motor for controlling the operation of the resistance varying means during coasting of the vehicle.

8. In a motor control system, in combination, a motor for propelling a vehicle, resistance varying means for controlling the motor current during acceleration or the vehicle, means for exciting the motor during coasting of the vehicle, switching means for establishing dynami braking nections for the motor to decelerate the vehicle, said resistance varying means being utilized to control the motor current during dynamic braking, and relay means responsive to the voltage of the motor for controlling the operation of the resistance varying means during coasting of the vehicle.

9. In a motor control system, in combination, a motor for propelling a vehicle, resistance varying means for controlling the motor current during acceleration of the vehicle, means for exciting the motor during coasting of the vehicle, switching means for establishing dynamic braking connections for the motor to decelerate the vehicle, said resistance varying means being utilized to control the motor current during dynamic braking, relay means responsive to the voltage of the motor for controlling the operation of the resistance varying means during coasting oi the vehicle, and means for governing the operation of said relay means.

10. In a motor control system, in combination, a motor for propelling a vehicle, resistance varying means for controlling the motor current during acceleration oi the vehicle, means for exciting the motor during coasting of the vehicle, switching means for establishing dynamic braking connections for the motor to decelerate the vehicle, said resistance varying means being utilized to control the motor current during dynamic braking, relay means responsive to the voltage of the motor for controlling the operation of the resistance varying means during coasting of the vehicle, and means associated with said resistance varying means for governing the operation of said relay means.

NORMAN H. WILLBY. 

